Due to electromagnetic factors, the influence of tooth space, current commutation, inductive reaction and others of the brushless permanent magnet brushless motor with the existing technology, a strong pulsating torque is produced. The torque pulsation caused by electromagnetic factors is the torque pulsation due to the interaction between stator current and rotor magnetic field, which is directly related to current waveform, counter EMF waveform and air gap flux density. Under ideal conditions, the stator current is square wave, the counter EMF waveform is trapezoidal, the flat-top width is 120° electrical angle, and the electromagnetic torque is constant. In the actual motor, because of the reason of design and manufacturing, the counter EMF waveform may not be trapezoidal wave, and the flat-top width may not be 120° electrical angle, which will cause the torque pulsation of the motor. Due to the existing of iron core groove tooth of the stator, the torque pulsation caused by tooth space makes the air-gap permeance on the surface of the permanent magnet and the corresponding stator not uniform. When the rotor rotates, in a state the magnetic circuit reluctance changes, thus causing the torque pulsation. Thus, the use of electric energy by the motor is not efficient.